JPH05110377A - Surface acoustic wave filter - Google Patents
Surface acoustic wave filterInfo
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- JPH05110377A JPH05110377A JP26412691A JP26412691A JPH05110377A JP H05110377 A JPH05110377 A JP H05110377A JP 26412691 A JP26412691 A JP 26412691A JP 26412691 A JP26412691 A JP 26412691A JP H05110377 A JPH05110377 A JP H05110377A
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- ground electrode
- electrode
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- input
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Abstract
Description
【０００１】[0001]
【産業上の利用分野】本発明は、通信等で特定周波数を
通過させるために使用される弾性表面波フィルタに関す
る。BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a surface acoustic wave filter used for passing a specific frequency in communication or the like.
【０００２】近年、車載用や携帯用の電話等の各種通信
装置の小型化、軽量化が進むに伴い、高周波数帯のフィ
ルタとして弾性表面波デバイスが使用されてきている。
従って、このようなフィルタは、通過帯以外減衰量を大
きくする必要がある。In recent years, surface acoustic wave devices have been used as filters in a high frequency band with the progress of miniaturization and weight reduction of various communication devices such as in-vehicle and portable telephones.
Therefore, in such a filter, it is necessary to increase the attenuation amount other than the pass band.
【０００３】[0003]
【従来の技術】図８に、従来の弾性波表面フィルタの構
成図を示す。図８において、弾性表面波フィルタ１
A は、例えば結晶方位がＹ軸３６°回転でＸ軸伝播のＬ
ｉＴａＯ3 （タンタル酸リチウム）の単結晶より形成さ
れる圧電基板２に、入力電極３及び出力電極がそれぞれ
接地電極（接続パッド）５に相対して、交互に配置され
る。すなわち、入力電極３は、入力接続パッド６より３
つの電極が延出しており、各電極間に２つの接地電極
（５ａ，５ｂ）が位置する。出力電極４は、出力接続パ
ッド７より２つの電極が延出し、各電極の両端に３つの
接地電極（５ｃ〜５ｅ）が位置する。そして、入力電極
３と出力側の接地電極５ｃ〜５ｅとがこれらより延出す
るくし形入力電極３ａを、また入力側接地電極５ａ，５
ｂと出力電極４とがこれらより延出するくし形出力電極
４ａを、互いに離間対向させてかみ合い状態で整合させ
て相対する。これら、入力電極３、出力電極４及びくし
形電極３ａ，４ａは、例えばアルミニウム等を圧電基板
２上に蒸着又はスパッタリングで金属層を形成し、フォ
トリソグラフィ技術により図８のパターンに形成するも
のである。例えば、くし形電極３ａ，４ａのピッチは９
００ＭＨｚの周波数帯の場合には約２．２μｍとなる。2. Description of the Related Art FIG. 8 is a block diagram of a conventional surface acoustic wave filter. In FIG. 8, the surface acoustic wave filter 1
A is, for example, L that propagates on the X axis when the crystal orientation is rotated by 36 ° on the Y axis
The input electrodes 3 and the output electrodes are alternately arranged opposite to the ground electrode (connection pad) 5 on the piezoelectric substrate 2 formed of a single crystal of iTaO 3 (lithium tantalate). That is, the input electrode 3 is connected to the input connection pad 6 by 3
Two electrodes extend, and two ground electrodes (5a, 5b) are located between the electrodes. Two electrodes of the output electrode 4 extend from the output connection pad 7, and three ground electrodes (5c to 5e) are located at both ends of each electrode. The input electrode 3 and the output-side ground electrodes 5c to 5e extend from the comb-shaped input electrode 3a, and the input-side ground electrodes 5a and 5e.
The comb-shaped output electrodes 4a from which b and the output electrode 4 extend are opposed to each other while being spaced apart from each other and aligned in a meshed state. The input electrode 3, the output electrode 4, and the comb-shaped electrodes 3a, 4a are formed by forming a metal layer on the piezoelectric substrate 2 by vapor deposition or sputtering and forming the metal layer in the pattern of FIG. 8 by the photolithography technique. is there. For example, the pitch of the comb-shaped electrodes 3a and 4a is 9
In the case of the frequency band of 00 MHz, it becomes about 2.2 μm.
【０００４】なお、両端のくし形入力入力電極３ａの両
最外端に帯域外抑圧度（減衰量）を良好ならしめるため
に反射くし形電極を配置する場合もある。In some cases, reflective comb-shaped electrodes are arranged at both outermost ends of the comb-shaped input input electrodes 3a at both ends in order to obtain good out-of-band suppression (amount of attenuation).
【０００５】一方、図９に、従来のカスケード接続され
た弾性表面波フィルタの構成図を示す。図９（Ａ）に示
す弾性表面波フィルタ１B は、図８における帯域外減衰
量を良好にするために２段のカスケード接続したもので
あり、図９（Ｂ）は、図９（Ａ）のＡ部分の拡大図であ
る。On the other hand, FIG. 9 shows a configuration diagram of a conventional surface acoustic wave filter connected in cascade. The surface acoustic wave filter 1 B shown in FIG. 9 (A) is a two-stage cascade connection for improving the out-of-band attenuation in FIG. 8, and FIG. 9 (B) is shown in FIG. 9 (A). It is an enlarged view of the A portion of FIG.
【０００６】図９（Ａ）において弾性表面波フィルタ１
B は、３入力２出力のものであり、入力電極１３は入力
接続パッド１６より３つの電極が延出しており、これら
と接地電極１５ａ〜１５ｃとが、それぞれくし形入力電
極１３ａを互いに離間対向させてかみ合い状態で整合さ
せて相対する。In FIG. 9A, a surface acoustic wave filter 1 is provided.
B has three inputs and two outputs, and three electrodes of the input electrode 13 extend from the input connection pad 16, and these and the ground electrodes 15a to 15c respectively separate the comb-shaped input electrodes 13a from each other and face each other. Then, they are aligned and face each other in a meshed state.
【０００７】また、出力電極１４は出力接続パッド１７
より３つの電極が延出しており、これらと接地電極１５
ａ〜１５ｃとが、それぞれくし形出力電極１４ａを互い
に離間対向させてかみ合い状態で整合させて相対する。The output electrode 14 has an output connection pad 17
3 electrodes are extended from these, and these and the ground electrode 15
a to 15c face each other with the comb-shaped output electrodes 14a spaced apart and opposed to each other and aligned in a meshed state.
【０００８】一方、入力電極１３及び出力電極１４のそ
れぞれの３つの電極間には接地電極１５ｄ〜１５ｇが配
置され、中間接続線１８ａ，１８ｂとの間で、くし形電
極１９ａ〜１９ｄを互いに離間対向させてかみ合い状態
で整合させて相対する。On the other hand, ground electrodes 15d to 15g are arranged between the three electrodes of the input electrode 13 and the output electrode 14, respectively, and the comb electrodes 19a to 19d are separated from each other between the ground electrodes 15d to 15g. They are opposed to each other and are aligned with each other in a meshed state.
【０００９】この場合、一部分を取り出せば、くし形入
力電極１３ａが一段目の入力電極となり、くし形電極１
９ａが一段目の出力電極、くし形電極１９ｄが二段目の
入力電極、１４ａが二段目の出力電極となる。In this case, if a part is taken out, the comb-shaped input electrode 13a becomes the first-stage input electrode, and the comb-shaped electrode 1
9a is the first-stage output electrode, the comb-shaped electrode 19d is the second-stage input electrode, and 14a is the second-stage output electrode.
【００１０】ここで、図９（Ｂ）に示すように、接地電
極１５ａと１５ｄとは導通状態で接地される。Here, as shown in FIG. 9B, the ground electrodes 15a and 15d are electrically grounded.
【００１１】[0011]
【発明が解決しようとする課題】ところで、図９に示す
ような弾性表面波フィルタ１B は、例えば８００ＭＨｚ
の周波数帯で使用する場合としては、帯域外減衰量が２
０〜３５ｄＢ、比帯域幅３％以上の特性を有する。By the way, the surface acoustic wave filter 1 B as shown in FIG.
When used in the frequency band of, the out-of-band attenuation is 2
It has characteristics of 0 to 35 dB and a specific bandwidth of 3% or more.
【００１２】しかし、通信機等の性能向上のためには帯
域外減衰量が３５〜５０ｄＢ必要であり、図９の弾性表
面波フィルタ１B では、入出力電極１３ａ，１４ａ間又
は次段との電極間で電圧が廻り込み、静電気的結合が大
きくなり、大幅な帯域外減衰量を得ることができないと
いう問題がある。However, in order to improve the performance of a communication device or the like, an out-of-band attenuation amount of 35 to 50 dB is required, and in the surface acoustic wave filter 1 B of FIG. 9, between the input / output electrodes 13a and 14a or the next stage. There is a problem in that a voltage spills between the electrodes, electrostatic coupling increases, and a large out-of-band attenuation cannot be obtained.
【００１３】そこで、本発明は上記課題に鑑みなされた
もので、電気的な結合を抑え、大幅な帯域外減衰量を得
る弾性表面波フィルタを提供することを目的とする。Therefore, the present invention has been made in view of the above problems, and an object thereof is to provide a surface acoustic wave filter that suppresses electrical coupling and obtains a large out-of-band attenuation.
【００１４】[0014]
【課題を解決するための手段】上記課題は、圧電基板上
に、入力電極及び出力電極と接地された入出力の接地電
極とを、くし形電極を互いに離間対向させてかみ合い状
態で整合させ、交互に多段で配設した弾性表面波フィル
タにおいて、１段及び次段の前記入力電極に整合された
前記入力接地電極と、前記出力電極に整合された前記出
力接地電極とを、それぞれ導通させると共に、該１段の
入力接地電極と該次段の出力接地電極とを分離すること
により解決され、適宜、該１段の入力接地電極及び出力
接地電極と、該次段の入力接地電極及び出力接地電極と
を分離し、又は、該１段の出力接地電極及び次段の入力
接地電極をそれぞれ非接地の中間電極とする。Means for Solving the Problems The above-mentioned problem is that, on a piezoelectric substrate, an input electrode, an output electrode, and a grounded input / output ground electrode are aligned in a meshed state with comb-shaped electrodes facing each other. In the surface acoustic wave filter arranged alternately in multiple stages, the input ground electrode aligned with the input electrodes of the first stage and the next stage and the output ground electrode aligned with the output electrode are electrically connected, respectively. This is solved by separating the first-stage input ground electrode and the second-stage output ground electrode, and the first-stage input ground electrode and output-ground electrode, and the second-stage input ground electrode and output-ground electrode as appropriate. The electrodes are separated from each other, or the output ground electrode of the first stage and the input ground electrode of the next stage are used as non-grounded intermediate electrodes.
【００１５】[0015]
【作用】上述のように、１段目及び次段の出力接地電極
及び入力接地電極を導通させ、一例として１段目の入力
接地電極と次段の出力接地電極とを分離する。As described above, the output ground electrode and the input ground electrode of the first stage and the next stage are made conductive, and as an example, the input ground electrode of the first stage and the output ground electrode of the next stage are separated.
【００１６】すなわち、入出力の接地電極を分離するこ
とは、入力電極に高周波電圧を印加した場合に、フィル
タ素子内で１段の出力電極や次段の入力電極等へ電圧の
廻り込みが抑えられる。これにより、大幅な帯域外減衰
量を得ることが可能となる。また、１段出力接地電極及
び次段の入力接地電極を非接地状態の中間電極とするこ
とによっても、フィルタ素子内での他電極への高周波印
加電圧の廻り込みが抑えられ、大幅の帯域外減衰量を得
ることが可能となる。In other words, the separation of the input and output ground electrodes means that when a high frequency voltage is applied to the input electrode, the sneak of the voltage to the output electrode of the first stage and the input electrode of the next stage in the filter element is suppressed. Be done. This makes it possible to obtain a large amount of out-of-band attenuation. Also, by using the first-stage output ground electrode and the next-stage input ground electrode as intermediate electrodes in the non-grounded state, it is possible to suppress the sneak of the high-frequency applied voltage to the other electrode in the filter element, and to significantly out-of-band. It is possible to obtain the amount of attenuation.
【００１７】[0017]
【実施例】図１に、本発明の一実施例の構成図を示す。
図１において、弾性表面波フィルタ３０は、３入力２出
力の多電極フィルタを２段にカスケード接続したもので
ある。圧電基板３１上に、入力パッド３２より３つの１
段目の入力電極３２ａが形成され、また、出力パッド３
３より３つの２段目の出力電極３３ａが形成される。DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a block diagram of an embodiment of the present invention.
In FIG. 1, a surface acoustic wave filter 30 is a three-input, two-output multi-electrode filter cascade-connected in two stages. On the piezo-electric substrate 31, three 1s from the input pad 32
The input electrode 32a of the stage is formed, and the output pad 3
Three output electrodes 33a of the second stage are formed from three.
【００１８】入力電極３２ａ及び出力電極３３ａは、接
地電極３４（３４ａ〜３４ｃ）と、くし形電極を互いに
離間対向させてかみ合い状態で整合される。この場合、
３４ａが１段の入力接地電極、３４ｂが２段の出力接地
電極、３４ｃが共通接地電極である。The input electrode 32a and the output electrode 33a are aligned with the ground electrode 34 (34a to 34c) in a meshed state with the comb electrodes facing each other. in this case,
34a is an input ground electrode of one stage, 34b is an output ground electrode of two stages, and 34c is a common ground electrode.
【００１９】一方、１段目の入力電極３２ａの間には接
地電極３４（３５ａ，３５ｂ）が形成され、１段目の出
力電極３６とくし形電極で整合される（図２において説
明する）。また、２段目の出力電極３３ａの間には接地
電極３７（３７ａ，３７ｂ）が形成され、２段目の入力
電極３８とくし形電極で整合される。なお、１段目の出
力電極３６は２段目の入力電極３８とは連絡線３９によ
り接続される。On the other hand, a ground electrode 34 (35a, 35b) is formed between the first-stage input electrodes 32a, and is matched with the first-stage output electrodes 36 by a comb-shaped electrode (described in FIG. 2). A ground electrode 37 (37a, 37b) is formed between the output electrodes 33a of the second stage, and is aligned with the input electrode 38 of the second stage by a comb-shaped electrode. The output electrode 36 of the first stage is connected to the input electrode 38 of the second stage by a connecting line 39.
【００２０】ここで、図２に、図１における接地電極の
第１の例の部分図を示す。図２において、１段目の入力
接地電極３４ａは接地電極３５ｂと導通され、１段目の
出力接地電極３５ａが共通接地電極３４ｃに導通され
る。なお、図示しないが、２段目の出力接地電極３４ｂ
は接地電極３７ｂに導通され、２段目の入力接地電極３
７ａが共通接地電極３４ｃに導通される。Here, FIG. 2 shows a partial view of a first example of the ground electrode in FIG. In FIG. 2, the first-stage input ground electrode 34a is electrically connected to the ground electrode 35b, and the first-stage output ground electrode 35a is electrically connected to the common ground electrode 34c. Although not shown, the second-stage output ground electrode 34b
Is connected to the ground electrode 37b, and the second input ground electrode 3
7a is electrically connected to the common ground electrode 34c.
【００２１】すなわち、１段目と２段目の入力接地電極
３４ａ，３７ａと出力接地電極３５ｂ、３４ｂを導通さ
せて、１段目の入力接地電極３４ａ（３５ｂ）と２段目
の出力接地電極３４ｂ（３７ａ）とを、共通接地電極３
４ｃに導通された１段目の出力接地電極３５ａ及び２段
目の入力接地電極３７ａから分離して共通接地しないよ
うにしたものである。That is, the input ground electrodes 34a, 37a of the first and second stages are electrically connected to the output ground electrodes 35b, 34b to make the input ground electrodes 34a (35b) of the first stage and the output ground electrodes of the second stage. 34b (37a) together with the common ground electrode 3
It is separated from the output ground electrode 35a of the first stage and the input ground electrode 37a of the second stage which are electrically connected to 4c so as not to be commonly grounded.
【００２２】このような弾性表面波フィルタ３０は、例
えば、厚さ５００μｍ、Ｙ軸３６°回転Ｘ軸伝播のＬｉ
ＴａＯ3 の圧電基板３１上に、上述の入力パッド３２、
出力パッド３３及びくし形の多電極を、ＡｌＣｕ（アル
ミニウム・銅）を２００ｎｍ程度にスパッタリングし
て、フォトリフソグラフィ技術により同時に形成するも
のである。この場合のくし形電極のピッチは通過させる
周波数帯により決定され、例えば９００ＭＨｚ周波数帯
の場合には約２．２μｍのピッチにされる。Such a surface acoustic wave filter 30 has, for example, a thickness of 500 μm, a Y-axis 36 ° rotation X-axis propagating Li.
On the piezoelectric substrate 31 of TaO 3 , the input pad 32,
The output pad 33 and the comb-shaped multi-electrode are simultaneously formed by photolithography technique by sputtering AlCu (aluminum / copper) to a thickness of about 200 nm. The pitch of the comb electrodes in this case is determined by the frequency band to be passed, and for example, in the case of the 900 MHz frequency band, the pitch is about 2.2 μm.
【００２３】なお、圧電基板３１の端部であって、接地
電極３４の両端に一般に配設されるくし形反射器を配置
してもよい。A comb-shaped reflector, which is generally arranged at the end of the piezoelectric substrate 31 and at both ends of the ground electrode 34, may be arranged.
【００２４】また、図３に、図１の配線の概念図を示
す。図３において、上述した弾性表面波フィルタ３０
は、キャンパッケージ（又はセラミックパッケージ）の
基台４１上に搭載され、入力パッド３２及び出力パッド
をピン端子４２ａ，４２ｂにワイヤ（例えばアルミニウ
ム）４３により接続される。また、接地電極３４，３
５，３７の分離されたそれぞれをワイヤ４３により基台
４１に接続されて、フィルタ特性を得るものである。Further, FIG. 3 shows a conceptual diagram of the wiring of FIG. In FIG. 3, the surface acoustic wave filter 30 described above is used.
Is mounted on a base 41 of a can package (or ceramic package), and the input pad 32 and the output pad are connected to the pin terminals 42a and 42b by wires (for example, aluminum) 43. In addition, the ground electrodes 34, 3
The separated wires 5, 37 are connected to the base 41 by wires 43 to obtain the filter characteristics.
【００２５】このような弾性表面波フィルタは、１段目
の入力電極３２ａに高周波電圧が加わると、弾性表面波
が励振され、１段目の出力電極３６に入射する。そこ
で、音響エネルギーは電気エネルギーに変換され、２段
目の入力電極３８に電気エネルギーが入力する。そし
て、再び電気エネルギーが音響エネルギー（弾性表面
波）に変換され２段目の出力電極３３ａに入射し、電気
信号が取り出される。In such a surface acoustic wave filter, when a high frequency voltage is applied to the input electrode 32a of the first stage, the surface acoustic wave is excited and enters the output electrode 36 of the first stage. Therefore, the acoustic energy is converted into electric energy, and the electric energy is input to the second-stage input electrode 38. Then, the electric energy is converted into acoustic energy (surface acoustic wave) again and is incident on the second-stage output electrode 33a, and the electric signal is extracted.
【００２６】一般に、導体間は容量結合しており、図１
に示す電極間には各段で静電的容量で結合されているこ
ととなる（図７参照）。従って、総ての接地電極３４，
３５，３７を圧電基板３１上で共通にすると、入力印加
電圧は、１段目の入力電極３２ａだけでなく、隣接する
１段目の出力電極３６や２段目の入力電極３８にも同時
に電圧が印加されることとなる。Generally, the conductors are capacitively coupled to each other as shown in FIG.
The electrodes shown in FIG. 7 are coupled by electrostatic capacitance at each stage (see FIG. 7). Therefore, all ground electrodes 34,
When 35 and 37 are commonly used on the piezoelectric substrate 31, the input applied voltage is applied not only to the first-stage input electrode 32a but also to the adjacent first-stage output electrode 36 and second-stage input electrode 38 at the same time. Will be applied.
【００２７】本発明の弾性表面波フィルタ３０は、接地
電極を上述のように圧電基板３１上で分離することによ
り、静電気的な結合容量が抑えられ、他の出力電極３６
や入力電極３８に廻り込む電圧を低減することができ
る。これにより、帯域外減衰量を３５〜４０ｄＢ程度
（図９は２０〜３５ｄＢ）に改善することができる（図
６、Ａ，Ｂ参照）。In the surface acoustic wave filter 30 of the present invention, by separating the ground electrode on the piezoelectric substrate 31 as described above, the electrostatic coupling capacitance is suppressed and the other output electrode 36.
It is possible to reduce the voltage flowing around the input electrode 38. As a result, the out-of-band attenuation amount can be improved to about 35 to 40 dB (20 to 35 dB in FIG. 9) (see FIGS. 6, A and B).
【００２８】次に、図４に、図１における接地電極の第
２の例の部分図を示す。図４は図１の共通接地電極３４
ｃを分離して共通接地電極３４ｃ1 ，３４ｃ2 としたも
ので、共通接地電極３４ｃ1 と１段目の出力接地電極３
５ａとを導通し、共通接地電極３４ｃ2 と２段目の入力
接地電極３７ａとを導通させたものである。Next, FIG. 4 shows a partial view of a second example of the ground electrode in FIG. FIG. 4 shows the common ground electrode 34 of FIG.
c is separated into common ground electrodes 34c 1 and 34c 2, and the common ground electrode 34c 1 and the first-stage output ground electrode 3
5a, and the common ground electrode 34c 2 and the second-stage input ground electrode 37a are electrically connected.
【００２９】すなわち、１段目の出力接地電極３５ａと
２段目の入力接地電極３７ａとを分離したものである。That is, the first-stage output ground electrode 35a and the second-stage input ground electrode 37a are separated.
【００３０】これによれば、電極間の静電気的な容量結
合がさらに抑えられ、他の出力電極３６や入力電極３８
に廻り込む電圧がさらに低減される。これにより、帯域
外減衰量を４０〜５０ｄＢまで改善することができる。According to this, the electrostatic capacitive coupling between the electrodes is further suppressed, and the other output electrodes 36 and the input electrodes 38 are
The voltage that goes around is further reduced. As a result, the out-of-band attenuation amount can be improved to 40 to 50 dB.
【００３１】また、図５に、図１における接地電極の第
３の例の部分図を示す。図５は、図１における共通接地
電極３４ｃを排除し、１段目の出力接地電極３５ａと接
地電極３５ｂとを導通すると共に、２段目の入力接地電
極３７ａと接地電極３７ｂを導通したものである。すな
わち、１段目の入力接地電極３４ａ及び１段目の出力接
地電極３５ａ（３５ｂ）と、２段目の入力接地電極３７
ａ（３７ｂ）及び２段目の出力接地電極３４ｂとを分離
したものである。Further, FIG. 5 shows a partial view of a third example of the ground electrode in FIG. In FIG. 5, the common ground electrode 34c in FIG. 1 is eliminated, the output ground electrode 35a of the first stage is electrically connected to the ground electrode 35b, and the input ground electrode 37a of the second stage is electrically connected to the ground electrode 37b. is there. That is, the first input ground electrode 34a and the first output ground electrode 35a (35b) and the second input ground electrode 37
a (37b) and the second-stage output ground electrode 34b are separated.
【００３２】これによれば、図４と同様に、帯域外減衰
量を４０〜５０ｄＢまで改善することができる。ここ
で、図６に、本発明帯域外減衰特性のグラフを示す。図
６において、破線Ａは図９に示す従来の帯域外減衰量２
０〜３５ｄＢであり、一点鎖線Ｂは図２の帯域外減衰量
３５〜４０ｄＢであり、実線Ｃは図４及び図５の帯域外
減衰量４０〜５０ｄＢを示している。According to this, similarly to FIG. 4, the out-of-band attenuation amount can be improved to 40 to 50 dB. Here, FIG. 6 shows a graph of the out-of-band attenuation characteristic of the present invention. In FIG. 6, a broken line A indicates a conventional out-of-band attenuation amount 2 shown in FIG.
0 to 35 dB, the alternate long and short dash line B indicates the out-of-band attenuation amount 35 to 40 dB in FIG. 2, and the solid line C indicates the out-of-band attenuation amount 40 to 50 dB in FIGS. 4 and 5.
【００３３】次に、図示しないが本発明の他の実施例を
説明する。この場合の実施例は、図２、図４及び図５に
おける１段目の出力接地電極３５ａ（３４ｃ）及び２段
目の入力接地電極３７ａ（３７ｂ）を非接地の中間電極
とするものである。すなわち、電気的に浮かせる状態と
したものである。Next, although not shown, another embodiment of the present invention will be described. In this embodiment, the first-stage output ground electrode 35a (34c) and the second-stage input ground electrode 37a (37b) in FIGS. 2, 4 and 5 are non-grounded intermediate electrodes. .. That is, it is in an electrically floating state.
【００３４】ここで、図７に、本発明の非接地の場合を
説明するための回路図を示す。図７において、前述した
ように、総ての接地電極３４ａ，３５ａ，３７ａ，３４
ｂが共通して接地されている場合には、各接地電極３４
ａ，３５ａ，３７ａ，３４ｂは静電気的な容量ＣO のコ
ンデンサが結合された状態と同じになる。Here, FIG. 7 shows a circuit diagram for explaining the non-grounded case of the present invention. In FIG. 7, as described above, all the ground electrodes 34a, 35a, 37a, 34
When b is grounded in common, each ground electrode 34
a, 35a, 37a, and 34b are the same as the state where the electrostatic capacitance C O capacitors are coupled.
【００３５】そこで、１段目の出力接地電極３５ａ（３
４ｃ）と２段目の入力接地電極３７ａ（３７ｂ）を非接
地とした場合、コンデンサが電気的に浮いた状態とな
り、高周波電源５０から１段目の入力電極３２ａに印加
される高周波電圧が１段目の出力電極３６及び２段目の
入力電極３８に廻り込むことが抑えられるものである。
これによる帯域外減衰量は、図４及び図５と同様に、図
６の実線Ｃに示す４０〜５０ｄＢまで改善することがで
きる。Therefore, the output ground electrode 35a (3
4c) and the second-stage input ground electrode 37a (37b) are not grounded, the capacitor is in an electrically floating state, and the high-frequency voltage applied from the high-frequency power source 50 to the first-stage input electrode 32a is 1 The output electrode 36 of the second stage and the input electrode 38 of the second stage are prevented from wrapping around.
The amount of out-of-band attenuation due to this can be improved to 40 to 50 dB shown by the solid line C in FIG. 6, as in FIGS. 4 and 5.
【００３６】[0036]
【発明の効果】以上のように本発明によれば、１段目及
び次段の出力接地電極及び入力接地電極を導通させ、１
段目の（入力）出力接地電極と次段の出力（入力）接地
電極を分離することにより、電極間の電気的な結合容量
を抑え、大幅な帯域外減衰量を得ることができ、通信機
等の性能を向上させることができる。As described above, according to the present invention, the output ground electrode and the input ground electrode of the first stage and the next stage are electrically connected to each other.
By separating the (input) output ground electrode of the second stage and the output (input) ground electrode of the next stage, the electrical coupling capacitance between the electrodes can be suppressed and a large out-of-band attenuation amount can be obtained. And the like can be improved.
【図１】本発明の一実施例の構成図である。FIG. 1 is a configuration diagram of an embodiment of the present invention.
【図２】図１における接地電極の第１の例の部分図であ
る。FIG. 2 is a partial view of a first example of a ground electrode in FIG.
【図３】図１の配線を示した概念図である。FIG. 3 is a conceptual diagram showing the wiring of FIG.
【図４】図１における接地電極の第２の例の部分図であ
る。FIG. 4 is a partial view of a second example of the ground electrode in FIG.
【図５】図１における接地電極の第３の例の部分図であ
る。FIG. 5 is a partial view of a third example of the ground electrode in FIG.
【図６】本発明の帯域外減衰特性のグラフである。FIG. 6 is a graph of out-of-band attenuation characteristics of the present invention.
【図７】本発明の非接地の場合を説明するための図であ
る。FIG. 7 is a diagram for explaining a non-grounded case of the present invention.
【図８】従来の弾性表面波フィルタの構成図である。FIG. 8 is a configuration diagram of a conventional surface acoustic wave filter.
【図９】従来のカスケード接続された弾性表面波フィル
タ構成図である。FIG. 9 is a configuration diagram of a conventional surface acoustic wave filter connected in cascade.
３０ 弾性表面波フィルタ ３１ 圧電基板 ３２ 入力パッド ３２ａ 一段の入力電極 ３３ 出力パッド ３３ａ ２段の出力電極 ３４ 接地電極 ３４ａ １段の入力接地電極 ３４ｂ ２段の出力接地電極 ３４ｃ 接地電極 ３５，３７ 接地電極 ３５ａ １段の出力電極 ３６ １段の出力電極 ３７ａ ２段の入力接地電極 ３８ ２段の入力電極 ３９ 連絡線 30 surface acoustic wave filter 31 piezoelectric substrate 32 input pad 32a one stage input electrode 33 output pad 33a two stage output electrode 34 ground electrode 34a one stage input ground electrode 34b two stage output ground electrode 34c ground electrode 35, 37 ground electrode 35a 1-stage output electrode 36 1-stage output electrode 37a 2-stage input ground electrode 38 2-stage input electrode 39 Communication line
Claims (4)
ａ）及び出力電極（３３ａ）と接地された入出力の接地
電極（３４，３５，３７）とを、くし形電極を互いに離
間対向させてかみ合い状態で整合させ、交互に多段で配
設した弾性表面波フィルタにおいて、 １段及び次段の前記入力電極（３２ａ，３８）に整合さ
れた前記入力接地電極（３５ａ，３７ａ）と、前記出力
電極（３３ａ）に整合された前記出力接地電極（３４
ｂ，３５ａ）とを、それぞれ導通させると共に、 該１段の入力接地電極（３４ａ）と該次段の出力接地電
極（３４ｂ）とを分離することを特徴とする弾性表面波
フィルタ。1. An input electrode (32) is provided on a piezoelectric substrate (31).
a) and the output electrode (33a) and the grounded input and output ground electrodes (34, 35, 37) are aligned in a meshed state by interlacing the comb-shaped electrodes so that they are opposed to each other. In the surface wave filter, the input ground electrodes (35a, 37a) matched to the input electrodes (32a, 38) of the first and second stages and the output ground electrode (34 matched to the output electrode (33a)
b, 35a) are electrically connected to each other, and the input ground electrode (34a) of the first stage and the output ground electrode (34b) of the next stage are separated from each other.
前記次段の入力接地電極（３７ａ）とを分離することを
特徴とする請求項１記載の表面波フィルタ。2. The one-stage output ground electrode (35a),
The surface acoustic wave filter according to claim 1, wherein the input ground electrode (37a) of the next stage is separated.
ａ）及び出力電極（３３ａ）と接地された入出力の接地
電極（３４，３５，３７）とを、くし形電極を互いに離
間対向させてかみ合い状態で整合させ、交互に多段で配
設した弾性表面波フィルタにおいて、 １段及び次段の前記入力電極（３２ａ，３８）に整合さ
れた前記入力接地電極（３５ａ，３７ａ）と、前記出力
電極（３３ａ）に整合された前記出力接地電極（３４
ｂ，３５ａ）とを、それぞれ導通させると共に、 該１段の入力接地電極（３４ａ）及び出力接地電極（３
５ａ）と、該次段の入力接地電極（３７ａ）及び出力接
地電極（３４ｂ）とを分離することを特徴とする弾性表
面波フィルタ。3. An input electrode (32) on a piezoelectric substrate (31).
a) and the output electrode (33a) and the grounded input and output ground electrodes (34, 35, 37) are aligned in a meshed state by interlacing the comb-shaped electrodes so that they are opposed to each other. In the surface wave filter, the input ground electrodes (35a, 37a) matched to the input electrodes (32a, 38) of the first and second stages and the output ground electrode (34 matched to the output electrode (33a)
b, 35a), respectively, and the one-stage input ground electrode (34a) and output ground electrode (3
5a) and the input ground electrode (37a) and the output ground electrode (34b) of the next stage are separated from each other, a surface acoustic wave filter.
次段の入力接地電極（３７ａ）のそれぞれを、非接地の
中間電極とすることを特徴とする請求項１乃至３記載の
弾性表面波フィルタ。4. The elastic surface according to claim 1, wherein each of the first-stage output ground electrode (35a) and the second-stage input ground electrode (37a) is an ungrounded intermediate electrode. Wave filter.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP26412691A JPH05110377A (en) | 1991-10-11 | 1991-10-11 | Surface acoustic wave filter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| JP26412691A JPH05110377A (en) | 1991-10-11 | 1991-10-11 | Surface acoustic wave filter |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| JPH05110377A true JPH05110377A (en) | 1993-04-30 |
Family
ID=17398837
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| JP26412691A Pending JPH05110377A (en) | 1991-10-11 | 1991-10-11 | Surface acoustic wave filter |
Country Status (1)
| Country | Link |
|---|---|
| JP (1) | JPH05110377A (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7283016B2 (en) * | 2004-06-30 | 2007-10-16 | Murata Manufacturing Co., Ltd. | Balanced acoustic wave filter and acoustic wave filter |
| US20160094200A1 (en) * | 2014-09-26 | 2016-03-31 | Wisol Co., Ltd. | Saw filter having ground terminals separated |
-
1991
- 1991-10-11 JP JP26412691A patent/JPH05110377A/en active Pending
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7283016B2 (en) * | 2004-06-30 | 2007-10-16 | Murata Manufacturing Co., Ltd. | Balanced acoustic wave filter and acoustic wave filter |
| US20160094200A1 (en) * | 2014-09-26 | 2016-03-31 | Wisol Co., Ltd. | Saw filter having ground terminals separated |
| US9680447B2 (en) * | 2014-09-26 | 2017-06-13 | Wisol Co., Ltd. | Saw filter having ground terminals separated |
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